In designing an optical waveguide core layer formation material for a hybrid flexible printed wiring board for optical/electrical transmission, for example, a cured product of the core layer formation material is required to have a higher refractive index than a cured product of a cladding layer formation material. Therefore, it is conventionally a general practice to use a highly aromatic resin component in the design of the formulation of the core layer formation material. For reduction of an optical loss at a wavelength of 850 nm, for example, the absorption peak of the optical waveguide core layer formation material should be substantially prevented from broadening to a wavelength of 850 nm from the short wavelength range. For this major purpose, it is a general practice in the design of the formulation to improve the transparency of the core layer formation material based on the purity of a resin component of the formation material, or to reduce the amount of a photopolymerization initiator to be used particularly for a photocurable resin material (PTL 1 and PTL 2).